The present invention relates to an electronic amplifier circuit. More particularly, the present invention relates to an improved amplifier driver circuit for driving a bidirectional electromechanical position translator having dual opposed coils.
Electromechanical position translators enjoy widespread use. One exemplary application is for positioning data transducers relative to concentric data storage tracks within rotating disk data storage equipment. In such applications, the translator may be a linear "voice coil" or it may be a rotary actuator. In either case, an electronic amplifier is required to convert electrical position information into driving current to power the translator and thereby move the data transducer to the selected data storage track, and to maintain the data transducer at the selected track during data read and write operations of the storage equipment.
Data transducer position translators in disk drives are designed to position the data transducer as rapidly as possible from one data track to another. Conventionally, the amplifiers driving such translators have applied considerable driving current thereto in order to bring about rapid change of position. Since the data track positions within the storage equipment are precisely defined and are packed very closely together to maximize storage capacity, the conventional amplifiers have been high power linear amplifiers. Such amplifiers have a number of drawbacks. One drawback is high power consumption. Another drawback is the presence of a quiescent steady-state current through the translator when it is "on track", which requires that the translator be capable of dissipating the considerable heat generated by the quiescent current.
Ideally, an amplifier for driving a position translator should be capable of a current saturation mode for applying a maximum driving current to the translator to cause it to move as rapidly as possible to a new position. The amplifier should be capable of a linear mode for providing precise increments of current to the translator to adjust it and maintain it in proper alignment at each intended position. And, the amplifier should pass no current through the translator so long as it remains in proper position. The present invention constitutes a practical realization of these ideal characteristics.